\def\Fdiag{%
\begin{picture}(18,18)\put(1,1){\line(1,0){16}}\put(1,1){\line(1,2){8}}%
\put(1,1){\line(3,2){12}}\put(17,1){\line(-1,2){8}}\put(17,1){\line(-3,2){12}}%
\put(9,17){\line(0,-1){16}}\qbezier(5,9)(9,-7)(13,9)%
\put(0.5,-0.5){1}\put(17,-0.5){2}\put(9.2,17){4}%
\put(13.2,9){6}\put(4.2,9){5}\put(9,-0.5){3}\put(9.2,7){7}%
\end{picture}}
